Neat News 306 (added 2016-11-01)
Trees against Pollution in Cities

© Ildar Sagdejev (Specious) [CC BY-SA 3.0]
You may have guessed but now it has been measured. Trees have a positive effect on the air quality by reducing the number of microscopic particles in the air by 7% to 24%. These particles are potentially harmful since they are breathed in with polluted air by people and may become trapped in their lungs.